Blastocystis hominis requires concomitant growth of bacteria for its own growth. A few strains have been successfully grown in the absence of live bacteria (axenic growth) after a period of adaptation, with heavy antibiotic presence to gradually eliminate the bacteria species. But this is rare. Most attempts at axenization are unsuccessful. B. hominis does not usually ingest bacteria for food, but depends on metabolites generated by bacteria. Progress: The ability to eliminate bacteria and fungi from the majority of B. hominis cultures is now fairly assured. The supplemental use of Ceftizoxime, Amikacin and Erythromycin was not successful, as the mixture was toxic to B. hominis. The use of Ceftizoxime and Vancomycin together, at 1000 meg/ml each, final concentration, was successful in eliminating residual Bacteroides species, but not the associated Mycoplasma. Amplutericin successfully removed fungus and yeast. The Mycoplasma species may derive from the horse serum used. This organism was not eliminated, even with full use of both antibiotic cocktails (five antibiotics). The use of more assured, Mycoplasma free horse sera, from Hyclone and Gibco, may answer this question. Our belief is still strong, however, that the Mycoplasm derives from the human GI tract.